Apatite

Chemical composition -- A family of phosphates
containing calcium, iron, chlorine, and several other elements
in varying quantities. The most common variety contains fluorine,
and fluorapatite is the main constituent in bones and teeth!

Sources -- Widely distributed, but Mexico is
the major source, especially of yellow apatite. Some 100+ carat
stones are known, but most are under 20 carats. Blue and violet
stones are the rarest and are usually under 2 carats.